Method of producing an elongated flexible hose-like explosive column



Oct. 17, 1961 M. A. COOK ET AL METHOD OF PRODUCING AN ELONGATED FLEXIBLE HOSE-LIKE EXPLOSIVE COLUMN Filed NOV. 6, 1943 Me/win A.Co0lr Robert 5. Done INVENTORS R0 C Woeizvman ATTORNEY U ited Stat s Paw METHOD OF PRODUCING AN ELONGATED FLEXIBLE HOSE-LIKE EXPLOSIVE COLUMN Melvin A. Cook, Woodbnry, Robert S. Done, 'Clarksboro,

and Roy C.'Woehrman, Wenonah, NJ., assignors to E. L du Pont de Nemours and Company, Wilmington, Del, a corporation of Delaware Filed Nov. 6, 1943, Sen-No. 509,202 5 Claims. (Cl. 86-1) 'lhis'inyention relates to a method ofpackaging explosives and more particularly to amethod of filling flexible elongated containers under such conditions as to obtain a firm column of explosive that still retains flexibility.

Commercial explosives and military explosives for demolition work are ordinarily packaged by tamping or extrusion into preformed shells, by enclosing regularly shaped charges in containers, and by like methods. Where long columns of explosive have been desired, these have been prepared by butting together shorter units to give the desired length. Such columns are rigid and inflexible as a rule and in many cases, where such lengths of explosive are to be loaded into boreholes, such rigidity is ad vant-ageous. In certain uses, for example, in various 7 25 inany way.

An object of the present invention is a novel method 30 of packaging explosives in elongated containers of restricted cross-section. A further object is such a method that produces a firm but flexible column of explosive. A still further object is a novel method of filling explosive compositions into flexible elongated containers while the compositions are in fluid state and causing such compositions to become solidified and firm: subsequently. Additional objects will 'be disclosed as the invention is described more at length hereinafter.

*We have found that the foregoing objects are accomplished, and a novel and useful product obtained, when we 1) prepare an explosive composition containing a normally solid ingredient and an additional ingredient in which said normally solid ingredient is substantially more soluble at elevated temperatures than at ordinary solid ingredient in the second ingredient to flow at an elevated temperature into an elongated container of re stricted cross-section, and (3) allow said solution to cool and solidify in its container. When such a composition is introduced into a flexible container, the final package possesses flexibility as .well as firmness and solidity.

In carrying out such a method of packaging explosives and producing elongatedcolumns of explosive, we may, for example, employ a normally solid explosive compound of potentially high velocity along with other material or materials having considerable solvent action for said explosive compound at elevated temperatures and less of such action at ordinary temperatures. As an example, we may use trinitrotoluene along with a dinitrotoluene, themixture melting below the fusion point of trinitrotoluene. Such a mixture at a temperature of around 67 C. would be in fluid form and would remain fluid even after the introduction of an additional explosive compound such as pentaerythritol tetranitrate into suspension in the melt. This fluid would be caused to flow, while still hot, into a flexible elongated container such as a length of rubber-hose. On cooling, the above mixture would solidify but would remain reasonably flexible s that the charge in its container could be butted against 10 supplying salt in heated water to form a saturatedor reasonably concentrated solution and introduce into suspension in this solution a normally solid, high velocity explosive compound. Suitable soluble salts for use would 'be ammonium nitrate or.sodium nitrate or the like, and pentaerythritol tetranitrate'is an advantageous explosive for such suspension. The above mixture in heated form could be caused to flow into a length of rubber hose or other flexible elongated container, either by gravity or preferably under pressure. Oncooling, a firm but flexible column of explosive would result.

The following examples show specific embodiments of procedures followed in carrying out the invention, It will 'be understood that these are by way of illustration only, and are not to be taken as limiting the invention Example I An explosive composition was used having the following final composition:

Percent Trinitrotoluene Pentaerythritol tetranitrate} (-50 Ammonium nitr 3- 5 Water 10.8 Starch 2.0 Aluminum (powdered) 20.0

In producing the explosive mixture, a concentrated ammonium nitratesolution was prepared by introducing the proper amounts of ammonium nitrate and water-into an openmetal container and heating to 67 -C. The

temperatures, (2) cause such solution of the'normaifi P w l r at v used was a very intimately mixed product resulting from coprecipitation of the two materials from a common solvent. This mixture, the aluminum powder and the starch were added together to the ammonium nitrate s0 lution and the whole was agitated vigorously to assure thorough incorporation. While still maintained at 67 (1., this fluid mixture was caused to flow under pressure into a rubber tubing of one inch diameter and to fill a 200 foot length thereofi The rubber tubing or hose had previously been preheated with steam. A pressure of 62 lbs. per square inch was used and the filling of the tubing required 2 minutes and 10 seconds. The rubber tubing was .in substantially horizontal position, during filling, and the explosive and container were then allowed to cool. A firm but flexible column of explosive was ob-f tained, which was adapted for demolition of objects sired or for use under water. The finished explosive was sensitive to a No. 5 cap and detonated at a velocity of about 5000 feet per second.

3 Example 11 Another explosive mixture was prepared in the same manner, having the composition:

Percent Trinitrotoluene Pentaerythritol tetranitrate} (O 50 blend) Ammonium nitrate 54.0 Water 13.5 Starch 2.5

The above mixture in fluid condition at a temperature of 65 C. was caused to flow under a pressure, increasing to 60 lbs. per square inch, into a 50 foot length of 2-ply garden hose of /2 inch diameter. A satisfactory, firm but flexible column of explosive resulted after cooling.

Example III A slightly lms viscous blend of the following composition was prepared in a manner similar to that of Example 1:

Percent Trinitrotoluene Pentaerythritol tetranitrate }(5050 blend) Trinitrotoluene 24.75 Ammonium nitrate 40.0 Water 10.0 Starch 0.25

Instead of forcing this explosive composition to flow under pressure into the container, it was caused to fiow by gravity at a temperature between 60 and 68 C. into a 25-foot length of rubber hose of 1%" diameter. A

firm, flexible column of high velocity explosive was obtained after cooling.

The above mixture at a temperature of around 67 C. was caused to flow under pressure into a length of rubber hose of 1%" diameter. The filled length of explosive was then allowed to cool, with the formation of a firm, flexible column, enclosed in a water-resistant package. The explosive had a density of 1.47. The explosive column was not cap-sensitive but could be completely detonated when primed by a 25 gram booster of a pentaerythritol tetranitrate-trinitrotoluene booster of a density of 1.40.

Example V An explosive mixture was prepared of the following composition:

Percent P f jm gi tetramtme} 50-50 blend) 45.0 Trinitrotoluene 45.0 Dinitrotoluene 10.0

The procedure comprised dissolving the trinitrotoluene in the dinitrotoluene at a temperature of 67 C. and mixing in the blend of pentaerythritol tetranitrate and trinitrotoluene as a suspension in the solution. The composition was caused to flow by gravity into a length of rubber tubing of 1%" diameter. On cooling, a firm flex? ible column of explosive was obtained, sensitive to a No.

4 8 cap, having a high velocity of detonation and a density of 1.48.

Our invention may be better understood by reference to the attached drawing, showing apparatus in which the mixing and extrusion of the explosive may take place. In carrying out the procedure described in Example 1, for example, a concentrated aqueous solution of ammonium nitrate is prepared by introducing the proper amounts of ammonium nitrate and water into the vessel 1 closed by the tightly fitting cover 2. The water and solution are brought to, and maintained at, a temperature of around 67 C. by means of the surrounding water jacket 3, within the outer container 4. The hot water enters this jacket at 5 and overflows at 6. The inlet for the components of the explosive composition is shown at 7, and the mixture of the remaining dry ingredients is added here, the aluminum powder, the blend of trinitrotoluene and pentaerythritol tetranitrate, and starch. By means of the paddle agitators 8, supported by shaft 9, thorough incorporation is effected and the blade mixer 10 keeps the sloping sides of the long part of the vessel free from crusted material. When the mixture is complete, it is in viscous fluid form and is caused to flow out through 11, the valve 12 being opened. If the flexible container is to be filled under pressure, air is caused to pass in through 13, the pressure being indicated by a gage (not shown). The rubber tubing or other type of flexible container '14 is attached to the connecting piece 10 at 15. In the drawing, the container is shown in substantially horizontal position with slight upward slope, as this has been found to be the most desirable position of the container in pressure loading. If the container is to be filled by gravity flow alone, the air line 13 is not opened and the connection at 15 is to a vertical length of hose or other tubing.

In choosing an explosive composition for use according to the invention, it has been stated that a normally solid ingredient is used, together with an additional ingredient in which the first ingredient is relatively soluble at elevated temperatures and less so at ordinary temperature. This normally solid ingredient may, if desired, be the sensitizing ingredient of the mixture when it is itself a velocity explosive compound. Pentaerythritol tetranitrate or its blends with other materials, trinitrotoluene, for example, or blends of trinitrotoluene with other high velocity explosive compounds may be used in this manner, dissolved in an organic solvent. Trinitrotoluene dissolved in dinitrotoluene serves as such material in Example 4, such mixtures being fluid at temperatures between 60 and 70 C. and solid but flexible at ordinary temperatures.

Our preferred type of composition, however, comprises an inorganic, oxygen-supplying salt dissolved in water as the fluid medium. Suitable salts of this nature are ammonium nitrate, sodium nitrate, calcium nitrate, ammo.- nium perchlorate, sodium perchlorate, sodium chromate, sodium permanganate, and the like. All these are watersoluble and have a considerably higher solubility at elevated than at lower temperatures. Desirably a suflicient amount of the oxygen-supplying salt will be used to form substantially a saturated aqueous solution. Our preferred composition utilizes a concentrated aqueous solution of ammonium nitrate, since this salt possesses high explosive strength itself, in addition to its oxidizing power and its other suitable characteristics. When ammonium nitrate is used, we find a suitable soluble salt-water ratio to be approximately 4 to 1 so that about an ammonium nitrate solution is formed. Desirably, water is present in an amount between 9% and 15%. Desirably, a viscosity-increasing ingredient is introduced also and we find starch very satisfactory for this purpose as it gelatinizes readily in ammonium nitrate solutions. Starch may be used in an amount between 0.1% and 4%. Other materials may be used for this purpose, however, for example, bentonitic clays in finely divided form, and the like.

l As normally -s olid ingredient andone not soluble in the fluidizing vagent, various high explosive compoundsmay be employed, including pentaerythritol tetranitrate, cyclotrimcthylenetrinitramine, ethylenedinitramine, tetryl, blends of trinitrotoluene with the above compounds of higher melting point, and many others. We find particularly advantageous a blend of trinitrotoluene with pentaerythritol tetranitrate where particular intimacy of contact of the two compounds is attained, for example, in cast blends, coprecipitated mixtures, and the like.

We find it advantageous in many cases to include a finely divided oxidizable metal compatible with water as an ingredient, for example, aluminum or magnesium, or metallic alloys such as ferro-silicon. Aluminum has been found to be very desirable, and contributes to the explosive power because of its high heat of combustion, being particularly eflfective in underwater use.

Our method comprises the loading of the explosive in flowable condition into a flexible container such as rubber hose or tubing, and this flow of the material may take place by gravity or under applied pressure. It will be understood that the amount of pressure for use will depend on the diameter of the container and the degree of fluidity of the mix, which in turn will be considerably dependent on the temperature. Trinitrotoluene is an ingredient of our preferred compositions, either by itself or blended with other explosive materials. Since it melts at slightly above 80 C., we find it desirable to use a temperature between 50 and 80 C. In the case where an ammonium nitrate solution is the fluidity medium, a temperature of solution and flow of 65 to 70 C. is suitable.

Any type of resistant, flexible material will serve as container for the explosive. A rubber or rubber-like material is particularly desirable in the case of explosives containing water-soluble ingredients because of its effective bar to water penetration; hence, such explosives in rubber tubing are well adapted for use in the presence of and under water. Other materials may likewise be used such as various plastics, leather, canvas and other fabrics. This flexible container may desirably be preheated before filling, e.g. by use of steam.

The advantages of our method will be apparent. It allows the loading of an elongated column without preforming of the container into a definite shape and without limiting the use of the final product to an area of predetermined form. Flexibility is assured, and complete water resistance may be obtained either by formulation of a water-resistant composition or by enclosure of the composition in a water-proof container. If the explosive is used in water, its degree of buoyancy can be controlled by varying the density of the explosive or by attachment of weighting or buoying means to the container. The ex- 1 0 ,1 ,4. H 7, Mug. uh r i P slve Package as dlscloseu is waved composltion at an elevated temperature below 11116 11161? r or destructive purposes on land or water or in air, whereever objects are to be blasted.

While the invention has been described at length, it will be understood that many variations in compositions, materials and methods of procedure may be made with out departure from the scope of the invention. In describing the invention, it has been stated at times that the explosive composition, after loading into the flexible container is allowed to cool and solidify. It will be understood, however, that complete solidification of all the concentrated salt solution does not necessarily take place but that a certain, relatively small amount of fluid may remain, which enhances the flexibility of the explosive column. We intend to be limited, therefore, only by the following patent claims.

We claim:

1. A method of producing an elongated flexible hoselike explosive column which comprises preparing an explosive composition by blending water-soluble, inorganic, oxygen-supplying salt, water in an amount between 9 and 15% of the entire composition sufiicient to dissolve a substantial proportion of-said salt at elevated temperatures, and at least one normally solid explosive nitrated organic compound; maintaining said composition at ,an elevated temperature below the melting point of said nitrated explosive compound, thereby dissolving the inorganic salt while the solid explosive nitratedorganic compound becomes suspended in the aqueous solution of said salt; flowing the mixture at said elevated temperature into a flexible elongated tubular container of internal diameter of at least V2 inch; cooling the mixture to produce a column of explosive, rendered flexible by the presence of residual water content.

2. A method of producing an elongated flexible hoselike explosive column which comprises dissolving ammonium nitrate in heated water in an amount between 9 and 15 of the entire composition to form a concentrated solution; introducing starch into said solution in an amount between 0.1% and 4% by weight of the entire mixture; mixing therewith a blend of trinitrotoluene with a high velocity explosive compound of higher fusion point; maintaining the mixture at a temperature between 50 and C.; flowing said mixture under pressure and in heated condition into a flexible elongated tubular container of internal diameter of at least /2 inch; cooling the mixture to produce a column of explosive rendered flexible by the presence of residual water content.

3. A method of producing an elongated flexible hoselike explosive column which comprises preparing an explosive composition by blending a water-soluble, inorganic, oxygen-supplying salt, water, in an amount between 9 and 15 percent of the entire composition suflicient to dissolve a substantial proportion of said salt at elevated temperatures, introducing a viscosity-increas ing ingredient into said solution, and blending therewith at least one normally solid nitrated organic explosive compound; maintaining said composition at an elevated temperature below the melting point of said nitrated explosive compound, thereby dissolving the inorganic salt while the solid nitrated organic compound becomes suspended in the aqueous solution of salt; flowing the mixture at said elevated temperature into a flexible elongated tubular container of internal diameter of at least 36 inch; and cooling the mixture to produce a column of explosiverendered flexible by the presence of residual water content.

4. A method of producing an elongated flexible hoselike explosive column which comprises preparing an explosive composition by blending a waterssoluble, inor-- ing point of said nitrated explosive compound thereby dissolving the inorganic salt while the solid nitrated organic explosive compound becomes suspended in the aqueous solution of said salt, heating a flexible elongated tubular container of internal diameter of at least k inch, flowing the mixture at said elevated temperature into said heated container; cooling the mixture to produce a column of explosive rendered flexible by the presence of residual water content.

5. A method of producing an elongated flexible hoselike explosive column which comprises preparing an explosive composition by blending a water-soluble, inorganic, oxygen-supplying salt, water, in an amount between 9 and 15 percent of the entire composition sufiicient to dissolve a substantial proportion of said salt at elevated temperatures, and at least one normally solid nitrated organic explosive compound; maintaining said composition at an elevated temperature below the melting point of said nitrated explosive compound, thereby dissolving the inorganic salt while the solid nitrated organic explosive compound becomes suspended in the aqueous solution of salt; flowing the mixture by means of gravity at said elevated temperature into a flexible elongated tubular container of internal diameter of at least 1% inches; cooling the mixture to produce a column of explosive rendered flexible by the presence of residual water content.

References Cited in the file of this patent UNITED" STATES -PATENTS 682,390 .Sehrader Sept. 10, 1901 882,154 Lheure Mar. 17, 1908 1,049,666 Burkard Jan. 7, 1913' 1,917,540

Pearsall July 11, 1933 OTHER REFERENCES Culver: High Explosives, London, 1918, pages 734 and 735.

Davis: Chemistry of Powder and Explosives, Vol. II, Wiley, 1943, page 395. r

A 5 M m lul *4 

